1. Field of the Invention
The present invention relates &o an image processing computer system for producing an original film for the plate-making art, for example, for arranging a number of color images to be printed in a desired layout.
1. Description of the Prior Art
FIG. 1 is a block diagram of a conventional image processing computer system. Referring to FIG. 1, this system comprises a scanning type image readIng unit 11 for photoelectrically scanning originals to read the image data of the originals, a magnetic disk unit 12 which is a storage medium which is fixedly and on-line connected to the image reading unit 11, a detachable, magnetic tape unit 13, an image editing unit 14 which is connected on-line to the magnetic disk unit 12 and to the magnetic tape unit 13 and has an interactive operating part 14a through which an operator edits and processes the image data in accordance with the desired layout, tone and the like of the originals, and a scanning type image recording unit 15, connected on-line to the magnetic disk unit 12, for scanning a photosensitive film by an exposure beam to record an image on the film in accordance with the image data edited by the image editing unit 14.
The image reading unit which has a function corresponding to the image reading part of well known electronic color scanner, continuously reads the image data of a number of originals, at a high speed. The read image data is written into the magnetic disk unit 12 which is capable of high speed and continuous access and has a large storage capacity. Image data to be ,edited is fetched from the magnetic disk unit 12 and transferred to an internal memory of the image editing unit 14 and thereafter edited by an operator through the interactive operating part 14a. The edited image data thus obtained is again written into the magnetic disk unit 12. After all the image data is edited and again stored in the magnetic disk unit 12, the edited data is outputted to the image recording unit 15. The image recording unit 15, which has a function corresponding to the image recording part of a well known electronic color scanner, scans a photosensitive film by an exposure beam to expose the film in accordance with the edited image data. The magnetic tape unit 18 is used for a backup unit for storing the read image data and the edited image data.
In the aforementioned image processing through the image processing computer system shown in FIG. 1, the percentage of total operating usage of the respective units 11, 14 and 15 are approximately 40%, 50%, and 10%, respectively. In this image processing computer system, the magnetic disk unit 12 is shared by the image reading unit 11, the image editing unit 14 and the image recording unit 15, and only one unit at a time may gain access to the disk unit 12. Therefore, image editing processing by the image editing unit 14 can not be performed when the image data read by the image reading unit 11 is written in the magnetic disk unit 12 and when the edited image data is readout from the magnetic disk unit 12 to the image recording unit 18. Thus, the image editing unit 14 has an idle time of 50% (40% +10%) of all the processing time.
Similarly, the image reading unit 11 has an idle time of 60% (50%+10%) of all the processing time. Time-division multiple access of the magnetic disk unit 12 by the image reading unit 11 and the image editing unit 14 is impossible, because the image reading unit 11 continuously scans a number of originals to continuously output the image data of the originals to the magnetic disk unit 12.
Further, image reading processing by the image reading unit 11 must be performed in a plurality of times in the case, for example, where some of originals to be read, which are unavailable at the beginning of the processing, are read by the image reading unit 11 in the middle of the processing. In such a case, image editing processing by the image editing unit 14 must be interrupted.
In general, an image processing computer system is extremely expensive, and hence it is desirable to decrease its idle time as much as possible, in order to increase productivity and decrease processing costs.
Although another type of an image processing computer system having a plurality of magnetic disk units 12a and 12b is proposed, as shown in FIG. 2, to perform image reading processing, image editing processing and image recording processing in parallel, such a system requires an additional expensive magnetic disk unit of high speed and large storage capacity, resulting in a high system cost.